Semiconductor device and its manufacturing method

Abstract

A semiconductor device is capable of being applied with both a positive and a negative voltage to its control gate, and writing to its memory requires a low voltage. A control gate is formed on a memory unit region of a field oxide film, and an inter-layer silicon oxide film is formed on its surface. A gate oxide film for a non-volatile memory is formed on a P substrate between N type diffusion layers. The floating gate is formed on the inter-layer silicon oxide film, the field oxide film, and the gate oxide film for the non-volatile memory. Since a large coupling ratio between the control gate and the floating gate is available on the field oxide film, memory rewriting requires only a low voltage. Further, since the control gate is formed by a poly silicon film, both a positive voltage and a negative voltage can be applied to the control gate.

Description

TECHNICAL FIELD [0001] The present invention generally relates to a semiconductor device and a manufacturing method thereof, and especially relates to a semiconductor device equipped with a non-volatile memory, and manufacturing method thereof. [0002] In this specification, a first electric conduction type is a P type or an N type, and a second electric conduction type is an N type or a P type, an electric conduction type reverse to the first electric conduction type, respectively. BACKGROUND ART [0003] As kinds of a non-volatile memory called EEPROM (electrically erasable programmable random memory), there are generally two kinds that are differentiated by quantities of gates. Namely, they are a one-layer gate type and a two-layer gate type. As for the one-layer gate type, technology has been available, such as presented by Japan Provisional Publications No. 6-85275 and No. 8-506693. As for the two-layer gate type, technology has been available, such as presented by Japanese Patent...

AI Technical Summary

Benefits of technology

[0027] A second object of the present invention is offering a manufacturing method that can reduce film thickness variation of both a gate oxide film for the memory, and a gate oxide film for transistors, such that the reliability is improved, when forming a non-volatile memory and other transistors simultaneously.

[0036] According to the first manufacturing method, the semiconductor device of the present invention can be manufactured. Further, both the gate oxide film for the transistor and the gate oxide film for the memory can be formed by the once-oxidized film, enhancing the reliability of the both gate oxide films, and reducing film thickness variation.

[0043] According to the second manufacturing method, the semiconductor device of the present invention can be manufactured. Further, both the low voltage endurance gate oxide film for the low voltage transistor and the gate oxide film for the memory are formed by the once-oxidized film, enhancing the reliability of the both gate oxide films, and reducing film thickness variation.

[0044] Further, since the gate electrode for the low voltage transistor and the gate electrode for the high-voltage transistor are formed separately from the floating gate, silicide processing by tungsten silicide etc. of the gate electrode for the low voltage transistor and the gate electrode for the high-voltage transistor is facilitated.

[0052] According to the manufacturing method, the semiconductor device of the present invention can be manufactured. Further, both the low voltage endurance gate oxide film for the low voltage transistor and the gate oxide film for the memory are formed with the once-oxidized film, enhancing the reliability of both gate oxide films, and reducing film thickness variation. Further, the high voltage endurance gate oxide film for the high-voltage transistor is formed with the twice-oxidized film, enhancing the reliability of the high voltage endurance gate oxide film, and reducing film thickness variation, compared with the conventional technology.

Problems solved by technology

Further, since the control gate is formed on the first insulation film, being electrically separated from the semiconductor substrate, both positive and negative voltages can be applied to the control gate, which is impossible in a conventional one-layer gate type non-volatile memory.

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